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      04-14-2011, 01:54 PM   #23
Grease Monkey
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Drives: 2011 E90 M3,1994 Euro E36 M3/4
Join Date: Apr 2006
Location: Fort McMurray, Alberta, Canada

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Originally Posted by mrad01 View Post
I saw the bearings out of my old engine, there were buggered. The engine had done 30,000 kms. It was a July 2007 build, so it did have the bad bearings and crank that they changed from Nov2008 onward.

Exactly what I am talking about!!!! You said your crank and main bearings were changed and the knock persisted. The cause of the knock and the bad bearings you saw out of your old engine were most likely not bad due to the bearings/crank themselves. It is quite possible the main bearing bores were out of round/tapered in your block which would cause bearing wear and noise and is also the reason why it persisted even after the bearings and crank was changed.

There are two proper ways to do repair a bearing/crank replacement on an engine diagnosed with bad main bearings.

1)Pull the engine out, put the bedplate back on the engine block, torque it down and then take measurements to verify everything is in spec. All of the new crank journals should also be measured to ensure they are in spec. Finally after this is done the bearings and crank should be installed, all mains should have plastigauge placed on them and the bedplate torqued. Once this is done and all of the measurements are within spec on the plastigauge, block and crank. You can be satisfied everything is ok. If this process is not followed then you are only assuming the block, crank and bearings is within spec. (The same process should be followed for the rod bearings, rods and journals but for the sake of this post I am only speaking about the mains)

2)The engine should be replaced with a complete long block. A long block will have all of the measurements I described above done during assembly so when you get it is "SHOULD" be good to go!

To me it seems that every dealer replacing crank and main bearings is not following the proper procedure and myself I would refuse to accept a dealer replacing crank and main bearings on my car without pulling the engine and verifying the block is within specs.
2011 E90 M3 ZCP - Individual Moonstone/Individual Amarone Extended/Individual Piano Black With Inlay:LINK!!!
1994 Euro E36 M3 Sedan - Daytona Violet/Mulberry:LINK!!!